Implant components and methods

ABSTRACT

Systems, devices, and methods are provided for orthopedic implants. The implants may include a base member, such as an acetabular shell or an augment, that is configured to couple with an augment, flange cup, mounting member, or any other suitable orthopedic attachment. Any of the implantable components may be include one or more porous surfaces. The porous surface may be textured by protrusions that connect to and extend from the surface. The sizes and concentration of the protrusions may be varied for specific applications to accommodate different implants and patient anatomies. A porous implant may also include one or more internal or external solid portions that strengthen the implant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/352,705, filed Jun. 8, 2010, U.S. ProvisionalApplication No. 61/352,722, filed Jun. 8, 2010, U.S. ProvisionalApplication No. 61/422,903, filed Dec. 14, 2010, and U.S. ProvisionalApplication No. 61/466,817, filed Mar. 23, 2011, which are herebyincorporated by reference herein in their entireties.

BACKGROUND

Joints often undergo degenerative changes due to a variety of reasons.When joint degeneration becomes advanced or irreversible, it may becomenecessary to replace the natural joint with a prosthetic joint.Artificial implants, including hip joints, shoulder joints, and kneejoints are widely used in orthopedic surgery. Specifically, hip jointprostheses are common. The human hip joint acts mechanically as a balland socket joint, wherein the ball-shaped head of the femur ispositioned within the socket-shaped acetabulum of the pelvis. Variousdegenerative diseases and injuries may require replacement of all or aportion of a hip using synthetic materials, typically metals, ceramics,or plastics.

More particularly, natural hips often undergo degenerative changes,requiring replacement of the hip joint with a prosthetic joint. Often,the hip is replaced with two bearing surfaces between the femoral headand the acetabulum. The first bearing surface is typically a prosthesisshell or acetabular cup, which may be formed of metal, ceramic material,or as otherwise desired. A liner (conventionally formed of polyethylenematerial such as ultra high molecular weight polyethylene, a ceramicmaterial, or in some cases, even a metal liner) is then fit tightlywithin the shell to provide an inner bearing surface that receives andcooperates with an artificial femoral head in an articulatingrelationship to track and accommodate the relative movement between thefemur and the acetabulum.

The cup (or a cup and liner assembly) is typically fixed either byplacing screws through apertures in the cup or by securing the cup withcement. In some cases, only a liner is cemented in a patient due to poorbone stock. In other cases, a cup having a porous surface may be pressfit into the reamed acetabular surface.

It may become necessary to conduct a second or subsequent surgery inorder to replace a prosthetic joint with a (often larger) replacementjoint. Such surgeries often become necessary due to further degenerationof bone or advancement of a degenerative disease, requiring removal offurther bone and replacement of the removed, diseased bone with a largeror enhanced prosthetic joint, often referred to as a revisionprosthesis. For example, bone is often lost around the rim of theacetabulum, and this may provide less rim coverage to securely place apress-fit cup. Such surgeries may thus be referred to as revisionsurgeries.

In acetabular revision surgery, an acetabular prosthesis generallyincludes additional mounting elements, such as augments, flanges, hooks,plates, or any other attachment or mounting points or members thatprovide additional support and/or stability for the replacementprosthesis once positioned. These additional mounting or attachmentmembers are often required due to bone degeneration, bone loss, or bonedefects in the affected area (in this instance, the hip joint).

Various types of these mounting members (which term is intended toinclude but not be limited to flanges, blades, plates and/or hooks) maybe provided in conjunction with a prosthesis system in order to help thesurgeon achieve optimal fixation, non-limiting examples of which includeiliac flanges (providing securement and fixation in and against theilium region of the pelvis), ischial blades (providing securement andfixation in and against the ischium), and obturator hooks (providingsecurement and inferior fixation by engaging the obturator foramen).Although there have been attempts to provide such mounting attachmentswith modularity, the solutions to date have generally fallen short ofproviding true modularity. Instead, they typically provide a fewdiscrete positions at which the mounting members may be positioned,without providing the surgeon a fuller range of decision options.

Additionally, in some primary surgeries and more often in revisionsurgeries, the acetabulum may have a bone defect or void that thesurgeon must fill with bone grafts before inserting a new shell. Thiscan be time consuming and expensive, and may subject the patient toadditional health risks. Some techniques use an augment in connectionwith the acetabular shell, which can be coupled to or otherwise attachedto the outer surface of the shell.

With current augments, the surgeon can attach the augment to the boneand then implant the cup. However, many acetabular shells rely on bonescrews to achieve proper fixation and the augment often gets in the wayof a screw. In short, surgeons need the freedom to place screws in thebest location, but this compromises their ability to use augments. Withcurrent systems, it also takes an increased amount of time surgical timeto trial the component orientation and then try to find good bonefixation for the cup. The surgeon will often have to free-hand theamount of bone removed while estimating the size of augment needed. Inthe cases where bone is often deficient, surgeons are hesitant to takeaway any more bone than necessary.

Various additional features and improved features intended for use andapplication with various types of joint implants are also describedherein, such as improved bone screws, improved coatings, and variousaugment removal and insertion options.

SUMMARY

Disclosed herein are systems, devices, and methods for providing modularorthopedic implants. The implants may include a base member, such as anacetabular shell or an augment, that is configured to couple with anaugment, flange cup, mounting member, any other suitable orthopedicattachment, or any combinations thereof. Mounting members include, forexample, flanges, blades, hooks, and plates. In some embodiments, theorthopedic attachments may be adjustably positionable about the basemember or other attachments thereby providing modularity for assemblingand implanting the device. Various securing and/or locking mechanismsmay be used between the components of the implant. In certainembodiments, the orthopedic attachments are removably coupled to thebase member or other components. In certain embodiments, the orthopedicattachments are integrally provided on the base member or othercomponents, yet may still be adjustably positionable thereabout. In someembodiments, expandable augments, base members, or other bone fillingdevices are provided. In some embodiments, surface features are providedthat create friction and allow for surrounding bone ingrowth at theinterface of the implants and a patient's bone.

Systems, devices, and methods described herein provide implants thatcreate friction and allow for surrounding bone ingrowth at the interfaceof the implants and a patient's bone. In certain embodiments, animplantable orthopedic device includes an implant that has a surfacethat contacts a patient's joint and has a plurality of protrusionsconnected to the surface that rise above the surface. The implant mayalso include pores dispersed throughout the surface at the boneinterface. The protrusions located at the surface of the implant may beblunt, or may be any other suitable shape and configuration. Theprotrusions may extend from the surface to any suitable height, such asheights between about 50 μm and about 2000 μm, heights between about 100μm and 1100 μm, or heights between about 200 μm and 400 μm. Theprotrusions may be spaced on the surface of the implant in any suitableconcentration or density. The desired protrusion density may also bepatient-specific, and may be determined based on the density of a nativebone into which a component is implanted. An implant may have a largenumber of protrusion features on its surface, and one or more of theseindividual features may fall outside of a desired size or spacingwithout affecting the overall efficacy of the surface.

In certain embodiments, an implant includes internal or externalstrengthening features. A porous implant may include internal orexternal strengthening ribs to provide support to surrounding porousstructures. A porous implant may also be coupled with a flange that hasa first end for attaching the flange to the implant and a second end forattaching the flange to surrounding bone structure. The porous implantmay also include a reticulated surface coating.

In certain embodiments, an implantable orthopedic device is created byproviding a mold having a negative impression of a porous beaded surfaceand providing an implant substrate to be coated. Particles areinterposed between the implant substrate and the mold, and a pressure orelevated temperature may be applied to the mold, implant substrate, andparticles. The implant substrate provided may be solid or may be porous,and the particles interposed between the implant substrate and the moldmay be symmetric or asymmetric.

In certain embodiments, an implantable orthopedic device is created bycreating a three-dimensional model simulating an outer surface profileof a porous beaded implant and creating a three-dimensional model of animplant substrate volume. The model simulating an outer surface profileof a porous beaded implant is applied to the model of an implantsubstrate volume to create a pre-form volume, and an algorithm isapplied to fill the pre-form volume with a desired reticulated structureto create a porous implant model. An implant is formed using the porousimplant model.

In certain embodiments, an implantable orthopedic device is created byproviding a mold of an implant having an inner surface mimicking anegative image of an outer surface profile geometry of a porous beadedsurface and providing a plurality of particles that are placed into themold. Pressure or elevated temperature is applied to the mold andparticles. The particles placed into the mold may be symmetric orasymmetric.

In certain embodiments, an implantable orthopedic device is created byproviding a mold of an implant having an inner surface mimicking anegative image of an outer surface profile geometry of a porous beadedsurface and loading one or more foaming agents into the mold. A porousfoam component is created in the general shape or size of the implantthat has an outer surface geometry mimicking an outer surface profilegeometry of a porous beaded surface. The porous foam component isremoved from the mold, and a binding agent is applied to the porous foamcomponent. A plurality of symmetric or asymmetric particles are appliedto the porous foam component having the binding agent and the porousfoam component, binding agent, and particles are subjected to anelevated temperature to sinter the particles together and burn out thefoam component to form an implant having a roughened porous texture withan outer surface profile geometry mimicking a clinically-proven porousbeaded structure. The porous foam component may be polymeric, and may bea polyurethane component.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 shows a first view of an illustrative implant component;

FIG. 2 shows a second view of an illustrative implant component;

FIG. 3 shows an illustrative implant coating volume having a sphericalbead surface profile;

FIG. 4 shows an illustrative unit cell having a porous structure;

FIG. 5 shows a cross-section of an illustrative coating volume with aspherical bead profile and a porous structure;

FIG. 6 shows a first illustrative SEM image of a porous surface; and

FIG. 7 shows a second illustrative SEM image of a porous surface.

DETAILED DESCRIPTION

To provide an overall understanding of the systems, devices, and methodsdescribed herein, certain illustrative embodiments will be described.Although the embodiments and features described herein are specificallydescribed for use in connection with acetabular systems, it will beunderstood that all the components, connection mechanisms, adjustablesystems, fixation methods, manufacturing methods, coatings, and otherfeatures outlined below may be combined with one another in any suitablemanner and may be adapted and applied to medical devices and implants tobe used in other surgical procedures, including, but not limited to:spine arthroplasty, cranio-maxillofacial surgical procedures, kneearthroplasty, shoulder arthroplasty, as well as foot, ankle, hand, andother extremity procedures.

Various implants and other devices described herein in their variousembodiments may be used in conjunction with any appropriatereinforcement material, non-limiting examples of which include bonecement, appropriate polymers, resorbable polyurethane, and/or anymaterials provided by PolyNovo Biomaterials Limited, or any suitablecombinations thereof. Further non-limiting examples of potentialmaterials that may be used are described in the following references:U.S. Patent Application Publication No. 2006/0051394, entitled“Biodegradable Polyurethane and Polyurethane Ureas,” U.S. PatentApplication Publication No. 2005/0197422, entitled “BiocompatiblePolymer Compositions for Dual or Multi Staged Curing,” U.S. PatentApplication Publication No. 2005/0238683, entitled “BiodegradablePolyurethane/Urea Compositions,” U.S. Patent Application Publication No.2007/0225387, entitled “Polymer Compositions for Dual or Multi StagedCuring,” U.S. Patent Application Publication No. 2009/0324675, entitled“Biocompatible Polymer Compositions,” U.S. Patent ApplicationPublication No. 2009/0175921, entitled “Chain Extenders,” and U.S.Patent Application Publication No. 2009/0099600, entitled “High ModulusPolyurethane and Polyurethane/Urea Compositions.” Each of the priorreferences is incorporated by reference herein in its entirety.

Referring now to FIGS. 1-7, certain embodiments provide componentshaving porous beaded coatings and methods for their manufacture. Becauseimplants and natural bone usually have different degrees of flexibility,uneven stress distributions may occur. Consequently, when an implant isloaded, there is generally some relative movement at the interfacebetween the bone (more compliant) and the implant (more rigid). Manyimplants thus employ an intermediate material such as bone cement toreduce the amount of relative movement; however, cementless implants mayrely on relative roughness to achieve the same goals.

Historically, small spherical beads, bundles of thin wires, andthermal-sprayed metal have been used to produce the friction necessaryto reduce the amount of relative movement. Optionally, screws and/orpress-fit features may improve the fixation of implant to bone. Suchtechnologies are generally accepted by the orthopedic surgeon community.However, the geometric nature of these coatings limits the location andsize of their porosity. Newer technologies, such as those that employasymmetric beads or metallic foams have improved the location and sizeof porosity, but they are difficult to manufacture with favorablesurface textures. Remedies have included placing hatch lines into thesurface of an already porous coating (e.g., via machining). Other poroussurfaces have been manufactured having sharp protrusions at amicroscopic level. These protrusions can cause problems when there iseven a small amount of relative movement between the bone and implant.The sharper protrusions can dig into the bone and create bone particlesor can break off from the implant and create wear particles at theimplant-bone interface. In addition to loosening the attachment betweenthe implant and bone, these loose particles can cause harmfulcomplications.

The shortcomings of previous porous surfaces are addressed by providingan implant having a surface that is textured with numerous bluntprotrusions on a macroscopic level and has a porous structure on amicroscopic level. The blunt protrusions create friction that reducesthe amount of relative movement between an implanted component andsurrounding bone. The porosity allows the surrounding bone to grow intothe implant, and the lack of relative movement between implant and bonefacilitates this ingrowth.

A consideration in designing and creating a porous implant having bluntprotrusions is the size and density of the protrusions. The protrusionscreate an area on which the bone initially contacts an implant. If theprotrusions are too large or spaced too far apart, the majority of theimplant's surface area between the protrusions will be too far from thebone for the bone to grow into the implant, and the bone may be unableto create a solid interface with the implant. In contrast, if theprotrusions are too small or located too close together, their effectwill be minimal and an implant may encounter the same problems as priorimplants with smoother surfaces or surfaces composed of manyconcentrated sharp protrusions. An ideal surface contains protrusionsthat are large enough to create the needed friction between the bone andimplant and still small enough to still allow for a high degree of boneingrowth into the porous surface. The protrusions may be any suitableheight, and preferably are between about 50 μm and about 2000 μm. Forcertain applications, it may be preferable to limit the protrusionheights to between 200 μm and 400 μm to achieve the desired level offriction and ingrowth with surrounding bone.

Protrusions on a surface of an implantable component may be any suitableshape or profile desired for a general or specific application of thecomponent. In certain embodiments, each surface protrusion may be a bumpshaped as a portion of a sphere above the surface of the implant.Protrusions may also be shaped like wires or any other suitablefeatures, including features common to cementless implants.

FIGS. 1 and 2 show some embodiments of an improved acetabular implant1500 which may be a whole augment, a portion of an augment, a flange, aplate, other mounting member, a shell, or a cage. The improvedacetabular implant 1500 mimics the bumpy outer surface geometries andprofiles of clinically-successful porous beads, with the roughness andporosity of a desired ingrowth interface. The surface of implant 1500 istextured by blunt protrusions 1502, which are shaped substantially ashemispherical bumps on the surface of implant 1500. The protrusions 1502are sized and spaced to create desirable friction that reduces movementof the implant 1500 relative to surrounding bone while allowing thesurrounding bone to grow substantially into the porous protrusions 1502and porous surface area 1504 between the protrusions. In addition to theprotrusion heights discussed above, the spacing and density ofprotrusions 1502 affect the amount of friction and bone ingrowthcreated. Any suitable density of protrusions 1502 may be used for animplant, and the protrusions preferably occupy between about 10% andabout 60% of the surface. The protrusions may be concentrated to adensity of between about 0.25 beads/mm² and about 6 beads/mm².

Improved acetabular implants, such as the implant 1500 of FIGS. 1 and 2,may be formed by any suitable approach, and may be formed using one ofthe following four methods.

A first method includes the steps of: 1) providing a mold having anegative impression of a porous beaded surface, 2) providing an implantsubstrate, which may be solid or porous, to be coated, 3) interposingsmall asymmetric particles between the implant substrate and said mold,and 4) applying a pressure and/or an elevated temperature to the mold,implant substrate, and small asymmetric particles to create a“green-state” implant (i.e., ready for full sintering) or a finalimplant (sintered), the implant having a roughened porous coating withan outer surface geometries and profiles mimicking a clinically-provenporous beaded structure with the roughness and porosity of a desiredtrabecular structure.

A second method includes the steps of: 1) creating a 3D model simulatingan outer surface profile of a porous beaded implant, 2) creating a modelof an implant substrate volume, 3) applying the 3D model simulating anouter surface profile of a porous beaded implant to the 3D model of theimplant substrate volume to create a bumpy pre-form volume, 4) applyingan algorithm to fill the bumpy pre-form volume with a desiredinterconnected porous or otherwise reticulated structure to create aporous implant model, and 5) creating an implant having a roughenedporous texture with an outer surface profile geometry mimicking aclinically-proven porous beaded structure using the implant model in arapid-manufacturing process.

A third method includes the steps of: 1) providing a mold of an implanthaving an inner surface mimicking a negative image of an outer surfaceprofile geometry of a porous beaded surface, 2) providing a plurality ofsmall asymmetric particles, 3) placing the plurality of small asymmetricparticles into the mold, and 4) applying a pressure and/or an elevatedtemperature to the mold and/or small asymmetric particles to create a“green-state” implant (i.e., ready for full sintering) or a finalimplant (sintered), the implant having a roughened porous texture withan outer surface profile geometry mimicking a clinically-proven porousbeaded structure.

A fourth method includes the creation of a beaded surface on a foamcomponent during the precursor step of making a metallic foam, themethod comprising the steps of: 1) providing a mold of an implant havingan inner surface mimicking a negative image of an outer surface profilegeometry of a porous beaded surface, 2) loading one or more foamingagents into the mold, 3) creating a porous foam component (e.g.,polymeric, polyurethane) in the general shape and/or size of saidimplant, which has an outer surface geometry mimicking an outer surfaceprofile geometry of a porous beaded surface, 4) removing the porous foamcomponent from the mold, 5) applying a binder or binding agent to theporous foam component, 6) applying a plurality of small symmetric orasymmetric particles (or a combination thereof) to the porous foamcomponent having a binder or binding agent thereon, 7) subjecting theporous foam component having binder or binding agent and particlesthereon to an elevated temperature to sinter the particles togetherand/or burn out the foam component to form a “green-state” implant(i.e., ready for full sintering) or a final implant (sintered), theimplant having a roughened porous texture with an outer surface profilegeometry mimicking a clinically-proven porous beaded structure. Implanthas a bumpy outer surface profile and geometries mimicking aclinically-proven porous-beaded structure.

The substrate forming at least an outer portion of the implant may be abulk porous, reticulated structure resembling a trabecular structure.One or more core portions or outer surface portions of the implant maybe solid (e.g., a portion of the implant may be configured forarticulation with another implant component). The implant may alsoinclude one or more solid internal portions. For example, implant 1500shown in FIG. 1 may include a solid structural portion on the interiorof the implant. The structural portion may be a single solid area ormultiple solid areas on the interior of implant 1500 that provide aseries of structural ribs to add support to the implant. The solidinternal structure may have any suitable shape and configuration, suchas a structural lattice similar to rebar in concrete. Illustrative butnon-limiting examples areas where the internal structure may be desiredinclude areas around screw holes, the equator region of an augment, orany other suitable area. In some embodiments, a polymer foam could bemelted or burned to have the shape of beads—or the foam could bepolymerized on a bead-shaped subsurface resulting in the end-producthaving a bead-shaped surface. In addition to solid internal components,implant 1500 may be coupled with external flanges or other mountingmembers to provide additional support to the implant. For example,implant 1500 may be implanted along with a flange that is attached tothe implant at a first end of the flange and attached to a patient'sbone at a second end, for example, with a bone screw secured into athrough-hole in the flange. Implant 1500 may also include external solidreinforcements, similar to common strut and brace structures, to providesupport to porous sections of the implant.

For rapid-manufacturing technologies, the bead surface geometries andprofile could be created virtually and subtracted out from a bulk porousentity or virtual beads could be created and combined with a porousentity. It is the general intent, in some, but not necessarily all,embodiments that the end-product be homogenous. Alternate embodiments ofimplants may include surface profiles that mimic metallic wire bundlesor the peaks and valleys of a thermal sprayed coating. Once a virtualmodel of the desired geometry is created using modeling software, animplant component having the desired surface profile can be createdusing any suitable rapid manufacturing techniques. For example, theporous implant can be created using 3D printing technology that usespowdered metal to “print” the modeled implant. In such an approach, afoam may be created having a surface profile that includes protrusions,such as protrusions 1502 in FIGS. 1 and 2, and the profiled foam maythen be filled in with powdered metal to create a porous microstructurewith the profiled surface. A foam that does not contain the protrusionsmay also be used to create the porous microstructure with powderedmetal, and the desired surface profile with protrusions can then bestamped into the surface of the porous metal implant.

Advantages of implants manufactured this way are that they containintegral porosity with the initially bone-engaging surface profile ofclinically-proven porous beads. In other words, the same featuresproviding the traction needed between bone and implant are the samefeatures providing a surface for bone to grow into and around for arigid and enduring fixation surface. As non-limiting examples, Tables Aand B show some examples of potentially suitable bead density (spacing),and diameter.

TABLE A Chart of number of beads in selected area and average andstandard deviation of bead diameter of 50 beads on a shell used with theBirmingham Hip ® Resurfacing system available from Smith & Nephew, Inc.in at least 3 fields of view (SEM, Jeol, Japan) Beads in 6.4 × BeadDiamter 4.8 mm area (mm) 11 Average D 1.24 20 Std D 0.12 20

TABLE B Percent solid for typical beaded product for bone ingrowth.Percent Product Company Implant Type Solid CoCr ROUGHCOAT Smith andProfix ® Femoral 46.3% (2-layer) Nephew CoCr Porocoat DePuy LCS ® KneeFemoral 46.5% (3-layer) CoCr Porocoat DePuy AML ® Stem 50.2% (3-layer)Ti ROUGHCOAT Smith and Synergy ™ Stem 51.9% (2-layer) Nephew Wherein,“percent solid” is a 2D measurement of bead density produced by typicalmetallographic techniques based on the test method disclosed in ASTMF1854, entitled “Standard Test Method for Stereological Evaluation ofPorous Coatings on Medical Implants,” which is incorporated by referenceherein in its entirety.

FIG. 3 shows a coating volume 1510 having spherical bead volumes 1512placed therein, such that the spherical bead volumes 1512 protrude fromthe coating volume 1510 to form a second coating volume mimicking aspherical bead profile. Alternatively, solid spherical beads may becombined into a porous coating. To create the coating volume 1510, twosoftware models can be created and then merged to form the final modelof the porous volume with the profiled protrusion surface. A first modelof a macroscopic structure of the volume, including the plurality ofbead volumes 1512, can be created in modeling software, and may looksubstantially the same as the volume shown in FIG. 3.

A second software model can be created to produce the porous microscopicstructure desired for a macroscopic volume, such as the volume shown inFIG. 3. FIG. 4 shows a unit cell 1520 of an exemplary porous reticulatedstructure, which may configured to fill the coating volume mimicking aspherical bead profile. The unit cell 1520 is made up of a complexstructure of struts 1512. The arrangement of struts 1512 creates voids1514 within unit cell 1520, thus making the desired porousmicrostructure. The size and arrangement of struts 1512 can be varied tocontrol the number and size of voids 1514. By controlling the size andarrangement of the struts 1512, a desired amount and profile of theporous structure is achieved.

FIG. 5 shows a cross section of a coating volume 1530, which maycorrespond to coating volume 1510 of FIG. 3, mimicking a spherical beadprofile after the volume has been replaced with a reticulated structure(e.g., via a repeating unit cell such as unit cell 1520 in FIG. 4 in CASsoftware, or using any of the 4 methods described above). The finishedcoating volume 1530 exhibits both the profiled macrostructure and porousmicrostructure. The dotted lines in FIG. 5 outline the surface profileof coating volume 1530 and show the protrusions that create a bumpysurface that produces friction with bone when implanted. Themicrostructure of coating volume 1530, made up of a combination of solidstructure 1532 and voids 1534, creates a porous implant into whichsurrounding bone can grow to fill in voids 1534 and create a solidmating of implant and bone.

FIG. 6 shows an SEM image 1540 taken at 25× magnification of the surfaceof a part made by the disclosed method. Surface topography is notapparent with this view. FIG. 7 is an SEM image taken 1550 at 50×magnification of the structure made with the disclosed method. Thestructures shown in FIGS. 6 and 7 exhibit the porous microstructurediscussed above with respect to coating volumes 1510 and 1530, and canbe created by merging a solid macrostructure with a porousmicrostructure model, such as the unit cell 1520 in FIG. 4.

As a further non-limiting example, the following chart shows someadditional exemplary parameters that have proven to be useful forvarious embodiments. In the chart below, MVIL refers to Mean VoidIntercept Length, which is another way of characterizing the averagepore size, particularly in structures where the pore shapes and sizesare not uniform. On generally known definition of MVIL is “measurementgrid lines are oriented parallel to the substrate interface. The numberof times the lines intercept voids is used with the volume percent voidto calculate the mean void intercept length.”

Electron Direct metal beam laser sintering Landon melting (SLS)Structure (EBM) Eurocoating EOS (FIG. 4) Avg. Strut Thickness (μm) —275-450 275-400 (360) (340) Avg. Pore Size: MVIL 300-920*  450-690 —(565) (560) Average Pore 900-1300* 1310 ± 280  1970 ± 40  Pore Window —370 ± 100 830 ± 150 Size: (μm) Not Specified 670-1340  600 ± 100 —*(fine, medium, and coarse structures)

It is generally desirable to provide between about 60-85% porosity. Poresizes may generally range between about 50-1000 microns. In the aboveexample, the smallest pore size provided was about 300 microns, and thesmallest window was about 595 microns across at its largest diameter. Itwill be understood that this example is intended to be non-limiting andprovided for illustrative purposes only.

The systems, methods, and devices described herein to create implantshaving both a profiled macrostructure and a porous microstructure canallow a medical professional to utilize customizable, patient-specificimplants. A customized implant can be efficiently created using therapid manufacturing techniques discussed herein by merging two or moremodels of an implant and then printing the modeled component. This couldallow a medical professional, such as an orthopedic surgeon, to order animplant specific to a single patient, including modeling the size andshape of the implant to fit defects or other unique features of thepatient's anatomy. This process can also be automated by taking bonescans of the patient's anatomy or using other available medical imagingand modeling techniques to automatically create a 3D model to use forrapid manufacturing.

The ability to customize an individual implant also allows a medicalprofessional to adjust the detailed macrostructure and microstructure ofthe implant to fit the needs of a particular application. For example,an orthopedic surgeon can adjust the macrostructure of the implant byselecting the shape, height, density, or other characteristics ofprotrusions on the surface of the implant. The surgeon can alsocustomize the number and size of voids within the implant to achieve adesired porosity for the implant. In some embodiments, the surgeon mayalso select the configuration of the macrostructure of the implant. Forimplants that include internal solid portions for strength andstructure, the surgeon can customize the size and location of theinternal solid portions to provide the structure in certain non-uniformareas of the implant where increased strength is needed. Illustrativebut non-limiting examples areas where increased strength may be desiredinclude areas around screw holes, the equator region of an augment,connection sites of augments, augment areas that are thinner thanothers, or any other suitable area. The surface profile of the implantcan also be non-uniform if different areas of the implant requiredifferent levels of friction or surface area for a bone interface. Asurgeon may want a higher concentration of surface protrusions incertain areas of the implant, such as areas that experience higherlevels of stress, and a lower concentration of protrusions, or noprotrusions at all, in other areas.

Porous implants described herein allow for an implant to provide goodcontact surface area and friction regardless of the quality of bone intowhich an implant is implanted. For example, patients who have softspongy bone may need features that are longer, and a lower number ofthose features. Patients with hard dense bone may require features thatare shorter, but a higher number of those features to create the samefixation in the bone. The specific requirements of a patient's anatomyand bone quality can be accommodated by the individualized designoptions provided by the porous implants described herein.

The foregoing is merely illustrative of the principles of thedisclosure, and the systems, devices, and methods can be practiced byother than the described embodiments, which are presented for purposesof illustration and not of limitation. It is to be understood that thesystems, devices, and methods disclosed herein, while shown for use inacetabular systems, may be applied to medical devices to be used inother surgical procedures including, but not limited to, spinearthroplasty, cranio-maxillofacial surgical procedures, kneearthroplasty, shoulder arthroplasty, as well as foot, ankle, hand, andextremities procedures.

Variations and modifications will occur to those of skill in the artafter reviewing this disclosure. The disclosed features may beimplemented, in any combination and subcombinations (including multipledependent combinations and subcombinations), with one or more otherfeatures described herein. The various features described or illustratedabove, including any components thereof, may be combined or integratedin other systems. Moreover, certain features may be omitted or notimplemented.

Examples of changes, substitutions, and alterations are ascertainable byone skilled in the art and could be made without departing from thescope of the information disclosed herein. All references cited hereinare incorporated by reference in their entirety and made part of thisapplication.

What is claimed is:
 1. A method for preparing an implantable orthopedicdevice, the method comprising: providing a mold having a negativeimpression of a porous beaded surface; providing an implant substrate tobe coated; interposing particles between the implant substrate and themold; and applying a pressure or elevated temperature to the mold,implant substrate, and particles to create an implant having a surfacethat matches the porous beaded surface of the mold and is formed fromthe interposed particles.
 2. The method of claim 1, wherein the implantsubstrate is solid or porous.
 3. The method of claim 1, wherein theparticles are asymmetric.
 4. A method for preparing an implantableorthopedic device, the method comprising: creating, with a processor, athree-dimensional model simulating an outer surface profile of a porousbeaded implant; creating, with the processor, a three-dimensional modelof an implant substrate volume; applying, with the processor, thethree-dimensional model simulating an outer surface profile of a porousbeaded implant to the three-dimensional model of an implant substratevolume to create a pre-form volume; applying, with the processor, analgorithm to fill the pre-form volume with a desired reticulatedstructure to create a porous implant model; and forming an implant usingthe porous implant model.
 5. A method for preparing an implantableorthopedic device, the method comprising: providing a mold of an implanthaving an inner surface mimicking a negative image of an outer surfaceprofile geometry of a porous beaded surface; providing a plurality ofparticles; placing the plurality of particles into the mold; andapplying a pressure or elevated temperature to the mold to form asurface that matches the porous beaded surface of the mold and is formedfrom the plurality of particles.
 6. The method of claim 5, wherein theparticle are asymmetric.
 7. A method for preparing an implantableorthopedic device, the method comprising: providing a mold of an implanthaving an inner surface mimicking a negative image of an outer surfaceprofile geometry of a porous beaded surface; loading one or more foamingagents into the mold; creating a porous foam component in the generalshape or size of the implant, the implant having an outer surfacegeometry mimicking an outer surface profile geometry of a porous beadedsurface; removing the porous foam component from the mold; applying abinding agent to the porous foam component; applying a plurality ofsymmetric or asymmetric particles to the porous foam component havingthe binding agent thereon; subjecting the porous foam component havingthe binding agent and particles thereon to an elevated temperature tosinter the particles together and burn out the foam component to form animplant, the implant having a roughened porous texture with an outersurface profile geometry mimicking a clinically-proven porous beadedstructure.
 8. The method of claim 7, wherein the porous foam componentis polymeric.
 9. The method of claim 8, wherein the porous foamcomponent is polyurethane.
 10. The method of claim 4, wherein thethree-dimensional model simulating an outer surface profile includesblunt protrusions on the modeled surface.
 11. The method of claim 10,wherein the modeled protrusions rise to a height between about 50 μm andabout 2000 μm.
 12. The method of claim 11, wherein the modeledprotrusions rise to a height between about 100 μm and about 1100 μm. 13.The method of claim 12,wherein the modeled protrusions rise to a heightbetween about 200 μm and about 400 μm.
 14. The method of claim 10,wherein the modeled protrusions are concentrated at between about 0.25particles per square millimeter and about 6 particles per squaremillimeter.
 15. The method of claim 10, wherein the porous implant modelhas a porosity between about 60% and about 85%.
 16. The method of claim10, wherein the modeled protrusions occupy between about 10% and about60% of the modeled surface profile.
 17. The method of claim 10, whereinmodeling the desired reticular structure comprises modeling, with theprocessor, a unit cell of the structure.
 18. The method of claim 17,wherein the unit cell includes interconnected modeled struts, with voidsdefined by the struts.
 19. The method of claim 18, wherein the modeledstruts have an average thickness between about 275 μm and about 400 μm.20. The method of claim 17, wherein applying the algorithm comprisesapplying, with the processor, the unit cell to the pre-form volume.